[Performance] Reworked how client to NPC aggro checks are made

- Before when reverse aggro checks were done (client to NPC), checks would happen every 750 millseconds where a client would
		check an entire entity list with distance calcs and other checks for aggro, with many clients in a zone and many NPC's this would
		add a lot of unecessary overhead. A temporary adjustment on 3/25 was made and upped the check to 6 seconds.
	- Now, there is a new methodology to scanning. The client will build a cache list of NPC's within close range as defined in new rule:
		RULE_INT(Range, ClientNPCScan, 300) and will also get any NPC that has an aggro range beyond that defined range to use in
		the frequent checks for aggro, the result is far less overhead
	- Client scanning changes when moving versus not moving, the client will scan aggro every 500 milliseconds while moving, and
		3000 millseconds aggro check when not moving, with a 6000ms re-fetch for close NPC's
	- A demo of these changes can be found here:
		https://youtu.be/aGroiwLSTVU

zone/client.h

@@ -221,6 +221,9 @@ public:
 	Client(EQStreamInterface * ieqs);
 	~Client();
 
+	std::unordered_map<NPC *, float> close_npcs;
+	bool is_client_moving;
+
 	//abstract virtual function implementations required by base abstract class
 	virtual bool Death(Mob* killerMob, int32 damage, uint16 spell_id, EQEmu::skills::SkillType attack_skill);
 	virtual void Damage(Mob* from, int32 damage, uint16 spell_id, EQEmu::skills::SkillType attack_skill, bool avoidable = true, int8 buffslot = -1, bool iBuffTic = false, eSpecialAttacks special = eSpecialAttacks::None);
@@ -1458,7 +1461,7 @@ private:
 	Timer forget_timer; // our 2 min everybody forgets you timer
 	Timer autosave_timer;
 #ifdef REVERSE_AGGRO
-	Timer scanarea_timer;
+	Timer client_scan_npc_aggro_timer;
 #endif
 	Timer tribute_timer;
 
@@ -1477,6 +1480,7 @@ private:
 	Timer helm_toggle_timer;
 	Timer light_update_timer;
 	Timer aggro_meter_timer;
+	Timer npc_close_scan_timer;
 
     glm::vec3 m_Proximity;